Oven for burning out invested models.



UNITED sTATEs PATENT OFFICE.

IHEODORE W. MAVES, 0F MINNEAPOLIS, MINNESOTA. i

OVEN FOR BURNING OUT INV ESTE-D MODELS.

Y i Specification of Letters Patent.

Patented sept. 24, 191s.

Application led April 24, 1918. Serial No. 230,451.

To all whom t may concern:

Be it known that I., TinioDoRE W. MAvEs a citizen of the United States, 'resident o' Minneapolis,county of Hennepin, State of Minnesota, have invented Certain new and useful Improvements in Ovens for Burning Out Invested Models, of which the Vfollowing and the sprue rod having been previously removeffl1 a matrix will be formed into which the molten metal is poured to form the de sired casting or inlay..r A I The object of my present invention 1s to provide improved means for melting the Wax model to the end that this part of the work can be Vneatly and expeditiously performed.'

I he invention consists generally 'in vari ous constructions and combinations, all as hereinafter described and particularly pointed out in the claims.

In the accompanying drawings forming part of this specification,

for closing the holes for the flasks when not Figure 1 is a vertical sectional view through an oven embodying my invention,

Fig. 2 is a plan view with the cover`re moved, showing the support for the flasks above the heater,

Fig. 3 is a plan view of the heater proper, Figs. 4t and 5 are detail vie Ws of the covers in use. y

rIn the drawing Qrepresents the base of 4the heatenhaving suitable supporting legs 3 and provided in its upper surface with a series of transverse grooves or recesses i in which a resistance coil 5 ispl'aced and embedded 1n a suitable plastic material 6. The

` ends ofthe coil are in circuit with an electric, ronduetoi 2` through which acurrent is pained to heat the resistance Wire 5 and the space above the heater forming the oven.

The resistance coil is so made or formed thatl when .the ':urrent is turned on the oven will be heated to a certain temperature which I have found best suited for melting the Wax andby equipping the heater with a coil for producing a certain degree "of temperature I am able to determine how long the ilask should he in the oven to melt themode1.

The base or bed of the heater has a recess or shoulder formed therein at 8 Whereon a casilig 0 is seated. rllhis casing is made pref-f erably oi metal, rectangular in form to fit snugly down .over the top of the base and l'orm a heating chamber -for the oven l() above the base. Ledges l1, preferably of anglo bar, are secured to the casing 9, preferabiy at a point midway between the top and bottom of the casing and form supports for a floor plate lthat is seated loosely on the ledges'll and forms the top or roof of the 1 oven chamber 10. .This plate 12 is provided' with a comparatively large central opening 13 and a series of smaller openings 14 arranged arouud it and I preferably provide Hanges l5 and 16 encircling these openings and spaced from the edges thereof to form ribs or ledges 17.` The flanges 15 and 16 have openings 18 therein and. cover plates 19 fit within the flanges and close the openings in the plate 12 and have ingerf grips 20 which project through the openings 18'. Those cover plates close the openings until such time as the operator desires to in sert a flask therein, when the plate will be removed and. the fiask, with the wax. model therein, placed in the opening with its lower portiondepending into the oven 10. The lower portion of the flask will be sufficiently near the top of the heater so that the wax wili be quickly melted and absorbed by the investing material. By providing openings of different sizes in the plate 12 I adapt it for flasks of different diameter, according to the size of the casting required. i

The top of the casing is closed byia cover plate 21 having a series of vent holes 22 therein, one above each opening, and a hand il t With this apparatus one or more flasks may be heated simultaneously `and the Wax models or patterns easily and quickly melted, leaving a matrix in each flask frdtn which the casting or inlay may be formed.

The flask supporting plate must be a certain predetermined distance from the heater to obtain the best results, but not too near or the Wax will be burned out or melted too quickly and if too far away the wax will be melted too slowly and too unevenly to obtain a` finely finished casting. A degree of heat that is too low to uniformly melt the Wax Will be fatal to the successful operation of the device for if the melting is not uni'- formly obtained the casting will not be smooth and will not be a duplicate of the wax pattern and hence will not fit the tooth. Over-heating will .cause 'the investment to crack and produce a defective casting. The best results are obtained by providing a slow, gradual heating of the oven and the Walls of the flask ,dependinof therein and by making provision for this slow, gradual heating I am able to produce a smooth, accurately formed casting which will be an exact duplicate of the Wax and be a perfect fitfor the tooth.

The device may be made in various sizes and the oven maybe modified in various ways and stillbe Within thescope of'iny 1nvention.

VI claim as my invention:

l. An apparatus of the class described,

comprisin a base having a heating means mounted t erein, a casing mounted on Said vrality of openings therein ada-pte base, andia flask supporting means arranged Within said easing and spacedv from said heatin means to form a dry heating chamber ino which the flask lcarried by said meansydepends.

'2;The combination, withV a base having an electric heating coil mounted therein, of \a\ l\thei\afor, casing surmounting said base, a late'sup-- ported Within lsaid casing interine iate to the top and bottom thereofand havin Jr a plu-v to i'ef ceive flasks for making dental castings, the space between said plate and said base forming a closed heating oven into which said flasks depend. A

3. The combination, with a base having a 'heating means mounted therein and a casing -surmounting said base, of a plate supported within ysaid casing and spaced from said base 'to form a heating oven, said plate having a plurality of holes therein and. flanges encircling said holes and spaced from the edges of said openings, and 'cover plates fitting casing Within said flanges and covering said openf ings, and a suitable cover for said casing.

4. An apparatus of the class described comprising ar base having an electric heater therein for producing a predetermined degree of heat, a casing supported by said base,

a flask carrier fitting Within said casing and j spaced from said heater to form an oven, said carrier having an opening therein to re- -ceive a flask containing a Wax model and in-A vestment material, said flask Adepending through said carrier into said oven and being heated by the predetermined degree of heat therein to melt said model.

5. An apparatus of the class described comprising a base having a' heating means mounted therein, a casing mounted on said base, 4a flask carrier arranged Within Saidcasing and spaced from said base to form an oven, and a fla-sk mounted in said carrier and depending.therethrough into said oven, said heating means being constructed to provide a gradual' uniform heat in said ven around the walls of thevflask depending therein.

6. An apparat-us of the class describedcomprising a base having an electric heating coil mounted therein for producing a predetermined degree of heat, a casing surmounting said base, a flask carrier supported vvith-- in said casing and spaced from said heater `to form an oven, said carrier having a com-l paratively large central opening therein and a series of smallerlopenings encircling said central opening a'daptedto receive flasks containing an investment material and Wax models, said flasks depending' into said oven and heated uniformly by said coil to melt said models in a predetermined time.

7. An apparatus of the class described comprising a base, an electric heat'ngcoil mounted therein, a casing supported byvsaidl base and having an l'open top and cover .and'siipportegl ipteriiiediate tothe top vand ottom thereof` and'A spaced from said heating coil asuflicient'distance to form an oven-which is closed to the escape of heat, said carrier having openings to receive flasks containing investment material and Wax models, saidlasks depending Within said oven and being subjected to the predeter` mined degree of heatV therein for melting the wax models in a given time, and said carrier having means for closing the openings therein which are not in use.

In witness Whereof,`I have hereunto set my hand this'29th dayof March 1918.

THEoDoiiE vv. MAvEs,

flask .carrier fitting within said inoo 

